[Plugin: WordPress SEO by Yoast] what's the tag for cust post type CATEGORY in title?

WordPress version: 3.4
WordPress SEO version: Version 1.2.4

I did this: put %%category%% for title to insert category name, BUT it’s a custom post type called “Products” and has its own product-category that’s different from the regular WP categories.

I expected the plugin to do this: insert the category into the title tag

Instead it did this: inserted nothing because I need a different code to put in that calls for the custom category for products.

Question:
What is the code to access a custom post type category for a title?

http://wordpress.org/extend/plugins/wordpress-seo/